Unfortunately, a "buffer state" wouldn't be enough: We need a true cordon sanitaire. Further, one could also regard Mexico as a staging area for Illegals from Central America.
Regards from Ba-Wü,
Would that be a Mex Kotex?
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)